Microwave energized plasma lamp with dielectric waveguide

ABSTRACT

A plasma lamp including a waveguide body consisting essentially of at least one solid dielectric material. The body is coupled to a microwave power source which causes the body to resonate in at least one resonant mode. A lamp chamber integrated into the body contains a fill mixture which forms a light-emitting plasma when the chamber receives microwave power from the resonating waveguide body. The chamber has an aperture sealed to the external environment by a window or lens allowing light to be transmitted. Alternatively, the fill is in a self-enclosed bulb positioned in the chamber. Embodiments disclosed include lamps having a drive probe and a feedback probe, and lamps having a drive probe, feedback probe and start probe, which minimize power reflected from the body back to the source both before the plasma is formed and after it reaches steady state.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/356,340filed on Jan. 31, 2003 and entitled “Microwave Energized Plasma LampWith Dielectric Waveguide,” which is a continuation-in-part ofapplication Ser. No. 09/809,718 (“'718”), filed on Mar. 15, 2001 andissued as U.S. Pat. No. 6,737,809 B2 and entitled “Plasma Lamp WithDielectric Waveguide”, which claimed benefit of priority of provisionalpatent application Ser. No. 60/222,028, filed on Jul. 31, 2000 andentitled “Plasma Lamp”. Application Ser. Nos. 09/809,718 and 60/222,028are incorporated herein in their entirety by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to devices and methods for generating light, andmore particularly to electrodeless plasma lamps energized by microwaveradiation. Rather than using a waveguide with an air-filled resonantcavity, embodiments of the invention use a waveguide having a bodyincluding at least one dielectric material with a dielectric constantgreater than approximately 2. Such dielectric materials include solidmaterials such as ceramics, and liquid materials such as silicone oil.The body is integrated with at least one lamp chamber containing a bulb.

2. Description of the Related Art

Electrodeless plasma lamps provide point-like, bright, white lightsources. Because electrodes are not used, they often have longer usefullifetimes than other lamps. Electrodeless lamps wherein microwave energyis directed into an air-filled waveguide enclosing or otherwise coupledto a bulb containing a mixture of substances that when ignited form alight-emitting plasma include: European Pat. App. EP 0 035 898 toYoshizawa et al.; and U.S. Pat. Nos. 4,954,755 to Lynch et al.,4,975,625 to Lynch et al., 4,978,891 to Ury et al., 5,021,704 to Walteret al., 5,448,135 to Simpson, 5,594,303 to Simpson, 5,841,242 to Simpsonet al., 5,910,710 to Simpson, and 6,031,333 to Simpson. U.S. Pat. No.6,617,806 B2 to Kirkpatrick et al. discloses a plasma lamp having acylindrical, metallic resonant cavity containing solid dielectricmaterial allowing a reduction in cavity size.

SUMMARY OF THE INVENTION

In a first aspect the present invention provides a lamp including awaveguide having a body including at least one dielectric material witha dielectric constant greater than approximately 2. A first microwaveprobe positioned within the body and connected to the source outputcouples power into the body from a microwave source operating at afrequency such that the body resonates in at least one resonant modehaving at least one electric field maximum. The body has at least onelamp chamber depending from a waveguide outer surface and having anaperture at that surface. The body and lamp chamber(s) form anintegrated structure. Each chamber contains a fill mixture including astarting gas and a light emitter, which when receiving power provided bythe resonating body forms a light-emitting plasma. Using a second probeor second and third probes positioned within the body, the inventionprovides means for minimizing power reflected back to the source when:(a) the source operates at a frequency such that the body resonates in asingle resonant mode; or (b) the source operates at one frequency suchthat the body resonates in a relatively higher order resonant modebefore a plasma is formed in each chamber, and at another frequency suchthat the body resonates in a relatively lower resonant mode after theplasma reaches steady state. The invention further provides alternativemeans for depositing the starting gas and light emitter within lampchambers, and alternative means for sealing chamber apertures to theenvironment while allowing light transmission.

In a second aspect the invention provides a lamp including a waveguidehaving a body including at least one dielectric material with adielectric constant greater than approximately 2. A first microwaveprobe positioned within the body is connected to an output of a sourceof microwave power operable at at least one frequency such that the bodyresonates in at least one resonant mode having at least one electricfield maximum. A second microwave probe, positioned within the body, isconnected to a source input. At least one lamp chamber, integrated withthe body, contains a fill mixture which when receiving power provided bythe resonating body forms a light-emitting plasma. The lamp furtherincludes means for minimizing power reflected from the body back to thesource.

In a third aspect the invention provides a lamp including a waveguidehaving a body including at least one dielectric material with adielectric constant greater than approximately 2. A first microwaveprobe positioned within the body is connected to an output of a sourceof microwave power operable at at least one frequency such that the bodyresonates in at least one resonant mode having at least one electricfield maximum. A second microwave probe, positioned within the body, isconnected to a source input. A third microwave probe is connected to thesource output. At least one lamp chamber, integrated with the body,contains a fill mixture which when receiving power provided by theresonating body forms a light-emitting plasma. The lamp further includesmeans for minimizing power reflected from the body back to the source.

A more complete understanding of the present invention and other aspectsand advantages thereof will be gained from a consideration of thefollowing description of the preferred embodiments read in conjunctionwith the accompanying drawing figures provided herein. In the figuresand description, numerals indicate the various features of theinvention, like numerals referring to like features throughout both thedrawings and description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, which is FIG. 1 of the '718 application, shows a sectional viewof a DWIPL including a waveguide having a body consisting essentially ofa solid dielectric material, integrated with a bulb containing alight-emitting plasma.

FIG. 2 schematically depicts a DWIPL having a body with a lamp chamberenclosed and sealed by a ball lens.

FIG. 3 schematically depicts a DWIPL having a body with a lamp chamberenclosed and sealed by a window or lens aligned with an optical elementattached to brackets attached to a flange extending from a heatsinksurrounding the body.

FIG. 4 schematically depicts a DWIPL having a cylindrical body attachedto a cylindrical heatsink with a bore which closely receives the body.

FIG. 5 schematically depicts a DWIPL having a cylindrical body enclosedwithin a “clamshell”-type heatsink.

FIG. 6 schematically depicts a DWIPL having a body with a tapped boreextending between a body side opposed to a side having a lamp chamberaperture, and the chamber bottom. A fill, including a starting gas andlight emitter, in the chamber is sealed by a window over the apertureand a plug screwed into the bore.

FIG. 7 schematically depicts the FIG. 6 DWIPL wherein the bore istapered and a tapered plug is press-fitted into the bore.

FIG. 7A is a detail view of the circled region “7A” in FIG. 7, showingthe plug tip and chamber bottom.

FIG. 8 shows first, second and third plug configurations for the FIG. 6DWIPL, and first, second, third and fourth plug configurations for theFIG. 7 DWIPL.

FIG. 9 schematically depicts a DWIPL having a body with a narrowcylindrical bore with a glass or quartz tube inserted therein, extendingbetween a body side opposed to a side having a lamp chamber aperture,and the chamber bottom. Fill in the chamber is sealed by a window overthe aperture and a glass or quartz rod inserted into the tube.

FIG. 10 schematically depicts a DWIPL having a body with a side having alamp chamber aperture covered by a window. Fill in the chamber is sealedby a glass or quartz rod inserted into a glass or quartz tube insertedinto a hole in the side in communication with a hole in a chamber wall.

FIG. 11 schematically depicts a DWIPL having a body with a side having alamp chamber aperture circumscribed by a groove in which is disposed anO-ring. Fill in the chamber is sealed by a window maintained in pressingcontact with the O-ring by a clamping mechanism.

FIG. 12 schematically depicts a DWIPL having a “U”-shaped body with asurface having a lamp chamber aperture circumscribed by a groove inwhich is disposed an O-ring. Fill in the chamber is sealed by a windowmaintained in pressing contact with the O-ring by a screw cap.

FIG. 13 schematically depicts a DWIPL having a body with a side having alamp chamber aperture circumscribed by a preformed seal. Fill in thechamber is sealed by a heated window which melts the seal when thewindow is brought into pressing contact with the seal by a hot mandrel.

FIG. 14 schematically depicts a DWIPL having a body with a side having alamp chamber aperture circumscribed by an attached first metallizationring and a preformed seal. Fill in the chamber is sealed when a secondmetallization ring attached to a window is brought into pressing contactthe first ring by a clamp and heat is applied to melt the preformedseal.

FIG. 15 schematically depicts the FIG. 14 DWIPL wherein a laser is usedto melt the preformed seal.

FIG. 16 schematically depicts the FIG. 14 DWIPL wherein the melting ofthe preformed seal results from inductive heating by an RF coil.

FIG. 16A is a top plan view of the FIG. 16 DWIPL.

FIG. 17A schematically depicts a DWIPL having a cylindrical body whereina bulb and a drive probe are located at the electric field maximum of aresonant mode.

FIG. 17B schematically depicts the FIG. 17A DWIPL wherein the bulb islocated at the electric field maximum of the FIG. 17A resonant mode, anda drive probe is offset from the maximum. The FIG. 17B probe is longerthan the FIG. 17A probe to compensate for coupling loss due to theoffset.

FIG. 18A schematically depicts a DWIPL having a rectangular prism-shapedbody wherein are disposed a bulb, and a drive probe and a feedback probeconnected by a combined amplifier and control circuit.

FIG. 18B schematically depicts a DWIPL having a cylindrical body whereinare disposed a bulb, and a drive probe and a feedback probe connected bya combined amplifier and control circuit.

FIG. 19 schematically depicts a first embodiment of a DWIPL utilizing astart probe. The DWIPL has a cylindrical body wherein are disposed abulb, a drive probe, a feedback probe, and the start probe. The feedbackprobe is connected to the drive probe by a combined amplifier andcontrol circuit, and a splitter, and is connected to the start probe bythe amplifier and control circuit, the splitter, and a phase shifter.

FIG. 20 schematically depicts a second embodiment of a DWIPL utilizing astart probe. The DWIPL has a cylindrical body wherein are disposed abulb, a drive probe, a feedback probe, and the start probe. The feedbackprobe is connected to the drive probe and the start probe by a combinedamplifier and control circuit, and a circulator.

FIG. 21A schematically depicts a third embodiment of a DWIPL utilizing astart probe. The DWIPL has a cylindrical body wherein are disposed abulb, a drive probe, a feedback probe, and the start probe. The feedbackprobe is connected to the drive probe and the start probe by a combinedamplifier and control circuit, and a diplexer.

FIG. 21B schematically depicts an alternative configuration of the FIG.21A embodiment wherein the feedback probe is connected to the driveprobe by a diplexer and a first combined amplifier and control circuit,and to the start probe by the diplexer and a second combined amplifierand control circuit.

FIG. 22A schematically depicts a DWIPL wherein a start resonant mode isused before plasma formation and a drive resonant mode is used to powerthe plasma to steady state. The DWIPL has a cylindrical body wherein aredisposed a bulb, a drive probe, and a feedback probe. A combinedamplifier and control circuit connects the drive and feedback probes.

FIG. 22B schematically depicts an alternative configuration of the FIG.22A embodiment wherein the feedback probe is connected to the driveprobe by first and second diplexers and first and second combinedamplifiers and control circuits.

FIG. 23 schematically depicts a DWIPL having a body with a highdielectric constant. A drive probe extending into the body is surroundedby a dielectric material having a high breakdown voltage.

FIG. 24 is a block diagram of a first configuration of the FIGS. 18A,18B, 22A and 22B combined amplifier and control circuit.

FIG. 25 is a block diagram of a second configuration of the FIGS. 18A,18B, 22A and 22B combined amplifier and control circuit.

FIG. 26 is a block diagram of a configuration of the FIGS. 19, 20, 21Aand 21B combined amplifier and control circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the present invention is open to various modifications andalternative constructions, the preferred embodiments shown in thedrawings will be described herein in detail. It is to be understood,however, there is no intention to limit the invention to the particularforms disclosed. On the contrary, it is intended that the inventioncover all modifications, equivalences and alternative constructionsfalling within the spirit and scope of the invention as expressed in theappended claims.

As used herein, the terms “dielectric waveguide integrated plasma lamp”,“DWIPL”, “microwave energized plasma lamp with solid dielectricwaveguide”, and “lamp” are synonymous, and the term “lamp body” issynonymous with “waveguide body”. The term “probe” herein is synonymouswith “feed” in the '718 application. The term “power”, i.e., energy perunit time, is used herein rather than “energy” as in the '718application. The terms “lamp chamber” and “hole” herein are synonymouswith “cavity” in the '718 application, and are used in describingconstruction details, such as seals and materials, of the several DWIPLembodiments disclosed. A “lamp chamber” is defined herein as areceptacle, i.e., hole, in a waveguide body having an aperture in a bodysurface which typically is coplanar with a waveguide surface exposed tothe environment. The term “bulb” denotes (A) a self-enclosed, discretestructure containing a fill mixture and positioned within a lampchamber; or (B) a “bulb envelope,” viz., a chamber containing a fillmixture and sealed from the environment by a window or lens. As usedhere, the term “fill” is synonymous with “fill mixture.” The term“self-enclosed bulb” is specific to meaning (A). The term “cavity” isused herein when describing microwave technology-related details such asprobe design, coupling and resonant modes. This change in terminologywas made because from an electromagnetic point of view a DWIPL body is aresonant cavity.

FIG. 1, copied from the '718 application, shows a “baseline” embodimentof a dielectric waveguide integrated plasma lamp to which theembodiments disclosed herein may be compared. DWIPL 101 includes asource 115 of microwave radiation, a waveguide 103 having a body 104consisting essentially of a solid dielectric material, and a drive probe117 coupling the source 115 to the waveguide, which is in the shape of arectangular prism determined by opposed sides 103A, 103B, and opposedsides 103C, 103D generally transverse to sides 103A, 103B. DWIPL 101further includes a bulb 107 of the (B) variety, disposed proximate toside 103A and preferably generally opposed to probe 117, containing afill 108 including a “starting” gas 108G, such as a noble gas, and alight emitter 108E, which when receiving microwave power at apredetermined operating frequency and intensity forms a plasma and emitslight. Source 115 provides microwave power to waveguide 103 via probe117. The waveguide contains and guides the energy flow to an enclosedlamp chamber 105, depending from side 103A into body 104, in which bulb107 is disposed. This energy flow frees electrons from the starting gasatoms, thereby creating a plasma. In many cases the light emitter issolid at room temperature. It may contain any one of a number ofelements or compounds known in the art, such as sulfur, selenium, acompound containing sulfur or selenium, or a metal halide such as indiumbromide. The starting plasma vaporizes the light emitter, and themicrowave powered free electrons excite the light emitter electrons tohigher energy levels. De-excitation of the light emitter electronsresults in light emission. Use of a starting gas in combination with asolid light emitter is not a necessity; a gas fill alone, such as xenon,can be used to start the plasma and to emit light. The preferredoperating frequency range for source 115 is from about 0.5 GHz to about10 GHz. However, operating frequencies as low as about 0.25 GHz and ashigh as about 30 GHz are feasible. Source 115 may be thermally isolatedfrom bulb 107 which during operation typically reaches temperaturesbetween about 700° C. and about 1000° C., thus avoiding degradation ofthe source due to heating. Preferably, the waveguide body provides asubstantial thermal mass which aids efficient distribution anddissipation of heat and provides thermal isolation between the lamp andsource. Additional thermal isolation of the source may be accomplishedby using an insulating material or vacuum gap occupying an optionalspace 116 between source 115 and waveguide 103. When the space 116 isincluded, appropriate microwave probes are used to couple the source tothe waveguide.

Due to mechanical and other considerations such as heat, vibration,aging and shock, contact between the probe 117 and waveguide 103preferably is maintained using a positive contact mechanism 121, shownin FIG. 1 as a spring loaded device. The mechanism provides a constantpressure by the probe on the waveguide to minimize the possibility thatmicrowave power will be reflected back through the probe rather thanentering the waveguide. In providing constant pressure, the mechanismcompensates for small dimensional changes in the probe and waveguidethat may occur due to thermal heating or mechanical shock. Preferably,contact is made by depositing a metallic material 123 directly on thewaveguide at its point of contact with probe 117 so as to eliminate gapsthat may disturb the coupling.

Sides 103A, 103B, 103C, 103D of waveguide 103, with the exception ofthose surfaces depending from side 103A into body 104 which form lampchamber 105, are coated with a thin metallic coating 119 which reflectsmicrowaves in the operating frequency range. The overall reflectivity ofthe coating determines the level of energy within the waveguide. Themore energy that can be stored within the waveguide, the greater thelamp efficiency. Preferably, coating 119 also suppresses evanescentradiation leakage and significantly attenuates any stray microwavefield(s). Bulb 107 includes an outer wall 109 having an inner surface110, and a window 111. Alternatively, the lamp chamber wall acts as thebulb outer wall. The components of bulb 107 preferably include at leastone dielectric material, such as a ceramic or sapphire. The ceramic inthe bulb may be the same as the material used in body 104. Dielectricmaterials are preferred for bulb 107 because the bulb preferably issurrounded by the body 104, and the dielectric materials facilitateefficient coupling of microwave power with the fill 108 in the bulb.Outer wall 109 is coupled to window 111 using a seal 113, therebydetermining a bulb envelope 127 which contains the fill. To confine thefill within the bulb, seal 113 preferably is a hermetic seal. Outer wall109 preferably includes alumina because of its white color, temperaturestability, low porosity, and low coefficient of thermal expansion.Preferably, inner surface 110 of outer wall 109 is contoured to maximizethe amount of light reflected out of cavity 105 through window 111.Preferably, window 111 includes sapphire which has high lighttransmissivity and a coefficient of thermal expansion which matches wellwith that of alumina. Window 111 may include a lens to collect and focusthe emitted light. During operation when bulb 107 may reach temperaturesof up to about 1000° C., body 104 acts as a heatsink for the bulb.Effective heat dissipation is achieved by attaching a plurality ofheat-sinking fins 125 to sides 103A, 103C and 103D.

When the waveguide body 104 consists essentially of a dielectricmaterial which generally is unstable at high temperature, such as atitanate, waveguide 103 may be shielded from the heat generated in bulb107 by interposing a thermal barrier between the body and bulb.Alternatively, outer wall 109 includes a material with low thermalconductivity, such as an NZP (NaZr₂(PO₄)₃) ceramic which acts as athermal barrier.

Although FIG. 1 shows waveguide 103 in the shape of a rectangular prism,a waveguide according to the invention disclosed in the '718 applicationmay be in the shape of a cylindrical prism, a sphere, or in any othershape that can efficiently guide microwave power from a drive probe to abulb integrated with the waveguide body, including a complex, irregularshape whose resonant frequencies preferably are determined usingelectromagnetic theory simulation tools. The waveguide dimensions willvary depending upon the microwave operating frequency and the dielectricconstant of the waveguide body. Regardless of its shape and size, awaveguide body preferably consists essentially of at least onedielectric material having the following properties: (1) a dielectricconstant greater than approximately 2.0; (2) a loss tangent less thanapproximately 0.01; (3) a thermal shock resistance quantified by afailure temperature greater than approximately 200° C.; (4) a DCbreakdown threshold greater than approximately 200 kilovolts/inch; (5) acoefficient of thermal expansion less than approximately 10⁻⁵/° C.; (6)a zero or slightly negative temperature coefficient of the dielectricconstant; (7) stoichiometric stability over a temperature range of about−80° C. to about 1000° C.; and (8) a thermal conductivity ofapproximately 2 W/mK (watts per milliKelvin). Ceramics having theseproperties as well as satisfactory electrical and thermo-mechanicalproperties include alumina, zirconia, certain titanates, and variationsor combinations of these materials. However, as disclosed in the '718application, one or more liquid materials having a dielectric constantgreater than approximately 2, such as silicone oil, may also be used.

High resonant energy within waveguide 103, corresponding to a highQ-value in the waveguide (where Q is the ratio of the operatingfrequency to the frequency bandwidth of the resonance), results in highevanescent leakage of microwave energy into lamp chamber 105. Suchleakage leads to quasi-static breakdown of the starting gas withinenvelope 127, thereby generating initial free electrons. The oscillatingenergy of the free electrons scales as Iλ², where I is the circulatingintensity of the microwave energy and λ is the wavelength. Thus, thehigher the microwave energy, the greater is the oscillating energy ofthe free electrons. By making the oscillating energy greater than theionization potential of the gas, electron-neutral collisions result inefficient build-up of plasma density. Once a plasma is formed and theincoming power is absorbed, the waveguide's Q-value drops due to theconductivity and absorption properties of the plasma. The drop inQ-value is generally due to a change in waveguide impedance. Afterplasma formation, the presence of the plasma in the lamp chamber makesthe chamber absorptive to the resonant energy, thus changing theimpedance. The change in impedance is effectively a reduction in theoverall reflectivity of the waveguide. By matching the reflectivity ofthe drive probe to be close to the reduced reflectivity of thewaveguide, a relatively low net reflection back into the energy sourceis realized. Much of the energy absorbed by the plasma eventuallyappears as heat. When the waveguide is used as a heatsink, thedimensions of the waveguide may change due to thermal expansion. If thewaveguide expands, the microwave frequency that will resonate within thewaveguide changes and resonance is lost. In order for resonance to bemaintained, the waveguide must have at least one dimension equal to aninteger multiple of the half-wavelength of the microwaves beinggenerated by source 115. Such dimensional changes can be compensated forby choosing a dielectric material for body 104 having a temperaturecoefficient for its refractive index that is approximately equal andopposite in sign to its coefficient of thermal expansion, so thatexpansion due to heating is at least partially offset by a change inrefractive index.

A lamp chamber in a DWIPL is a shaped hole in the solid dielectric lampbody. The hole is covered with a transparent window or lens to keep thefill mixture inside, which typically is a noble gas or a mixture of anoble gas such as argon and a salt or halide such as indium bromide orindium iodide. The cross-section of the hole at the lamp body surfacefrom which the hole depends is termed the “aperture.” An aperture can becircular, rectangular, or an arbitrary shape. The three-dimensionalshape of the chamber hole can be: a regular prism whose cross-sectionhas the same shape as the aperture, e.g., a cylindrical prism and acircular aperture; a regular prism whose cross-section is shapeddifferently than the aperture, so that there is a transition regionproximate to the aperture; or an arbitrary shape. A lamp chamber bottomcan be shaped to serve as a light reflector, so that light striking thebottom is reflected toward the aperture. Specifically, a bottom can beshaped as a paraboloid, an ellipsoid, a chiseled prism, or with one ormore curvatures tailored for a specific application.

A lamp chamber can be shaped to provide desired characteristics of theemitted light. For example, the chamber can be a cylinder with adiameter optimally chosen to match the dimensions of a light collectingapparatus connected to the lamp. The diameter is constrained at a lowerlimit by the requirement that the mean free path of an energizedelectron be long enough that sufficient electron-ion collisions occurbefore the electron strikes the chamber wall. Otherwise, the resultingefficiency will be too low. The diameter is constrained at an upperlimit dependent on the lamp operating frequency. Otherwise, microwaveenergy will be emitted through the aperture.

A typical requirement for a lamp used in an application such as aprojection television set is to make the chamber have an “opticalextent” (or “etendue” E) which depends on the aperture area A and anf-number (“f#”), characterizing the cone angle of the emitted light,which depends on the ratio of the diameter to the chamber depth.Specifically, E=πA/4(f#)². Typically, the depth is selected to achieve adesired f#, with a greater depth resulting in a smaller f# and a smalleretendue. For a very deep chamber, light emitted toward the chambermiddle or bottom may tend to hit the chamber wall and be absorbed,reducing the net efficiency of the lamp. For a very shallow chamber,light may be emitted in too broad a cone angle.

A lamp chamber may include a discontinuity in shape to provide anelectric field concentration point (see FIGS. 7A and 8) which tends tofacilitate breakdown of the fill mixture when the lamp is off, resultingin easier starting. Such a discontinuity can be a cone- or cup-shapeprojecting from the chamber bottom or side. Alternatively, adiscontinuity can be formed by a deliberately added object, such as afill tube end extending into the chamber.

There can be several lamp chambers in the same lamp body. The chambersare located at electric field maxima which exist for the selectedwaveguide operating mode. Preferably, a mode is selected which allowsthe chambers to be disposed in a configuration useful for providinglight to each of several different optical paths. Each chamber cancontain the same fill mixture, or the mixtures can be different. Thus,the spectrum of light emitted from each chamber can be the same, or thespectra can be different. For example, a lamp having three chambers,each with a unique fill mixture, could emit from each chamber,respectively, primarily red, blue and green light, so that the lightfrom each chamber could be used for a separate channel of ared-blue-green optical engine. Alternatively, each chamber could containthe same fill mixture so that multiple independent sources would beavailable for related but separate uses.

A lamp body can essentially consist of more than one solid dielectricmaterial. For example, a lamp body can have a small volume around thelamp chamber made of alumina, to take advantage of its good mechanical,thermal and chemical properties, with the rest of the body made of amaterial with a higher dielectric constant than that of alumina butwhich does not have thermal, mechanical and/or electrical propertiesadequate to contain a plasma. Such a lamp would be a smaller than a lamphaving an all-alumina body, likely would operate at a lower frequencythan an all-alumina lamp of the same size, and would be less expensiveto manufacture since it would require less high dielectric constantmaterial.

The electromagnetic design of a lamp body having more than one soliddielectric material is performed in iterative steps. Firstly, a roughlamp shape is selected and an electromagnetic analysis and simulationperformed for a lamp body consisting of the material occupying thegreatest amount of body volume. Secondly, the simulation results areassessed to determine how close the lamp is to the desired operatingfrequency. Thirdly, the simulation is repeated with the severaldielectric materials included in the simulated structure. Using theanalysis results, the dimensions are adjusted and the simulationrepeated until the body has the desired combination of operatingfrequency, size and proportions of materials.

A lamp body with several dielectric materials can be designed to includea layer, such as an evacuated space, inert gas, or a solid material,between two materials to serve as a thermal barrier. An evacuated spacecontributes to thermal management by increasing the temperature of thechamber wall(s), and providing a region in which the net lamp thermalflow rate results in a greater temperature differential than without theevacuated space (see FIGS. 3A and 3B of the '718 application).

One or more mechanical elements are required to enclose and seal a lampchamber against the high thermomechanical stresses and pressures createdby a plasma. Referring to FIG. 2, a DWIPL 200 includes a body 202 havinga side 204 with a surface 204S from which depends a lamp chamber 206having an aperture 208. A ball lens 210 is attached to surface 204S by aseal 212. Preferably, lens 210 is made of sapphire. Indicium 220 showsthe direction of light emitted from chamber 206.

A window or lens enclosing and sealing a chamber can be coupled to otheroptical elements which collect, process and direct lamp light output.Examples include a tube lined with a reflective material or coating, anda light pipe. Such optical elements can be mounted to bracketsintegrally attached to a heatsink around a lamp body, providing a lowcost, high integrity way to mount and attach optical components to thelamp. Referring to FIG. 3, a DWIPL 300 includes a body 302 having a side304 with a surface 304S from which depends a lamp chamber 306 having anaperture 308. Body 302 is enclosed by a “U”-shaped heatsink 310 having acentral portion 312 attached and generally orthogonal to opposed,generally parallel first and second portions 314, 316, respectively,having, respectively, ears 314E, 316E generally orthogonal to portions314, 316 and attached to opposed first and second lamp mounting panels318, 320, respectively. Portion 314 extends in a flange 322 to which arerigidly attached generally opposed first and second brackets 324, 326generally orthogonal to the flange 322. A window/lens 330 attached tosurface 304S and covering aperture 308 encloses and seals the chamber306. An optical element 332, such as a light pipe, is rigidly attachedto the brackets 324, 326 and aligned with window/lens 330. Indicium 334shows the direction of light output from element 332.

A DWIPL can consist of a single integrated assembly including: a lampbody with a sealed lamp chamber; a driver circuit and driver circuitboard; a thermal barrier separating the body and driver circuit; and anouter heatsink. Alternatively, separate packages are used for: (a) thelamp body and heatsink; and (b) the driver circuit and its heatsink. Fora DWIPL utilizing two probes (see FIGS. 15A and 15B, and FIG. 6 of the'718 application), the body and driver circuit are connected by two RFpower cables, one connecting the output of the driver circuit to thebody, and the other providing feedback from the body to the drivercircuit. The use of two separate packages allows greater flexibility inthe distribution of lamp heat and lamp driver heat. This may enable aprojection television or other device to be built without including afan for the lamp. Such two-package configurations may also enable designof television sets having smaller depth in the critical dimension fromviewing screen to back panel than has heretofore been achieved.

A DWIPL offers substantial advantages for heat removal because the soliddielectric material(s) used for the lamp body can be chosen forcharacteristics which result in heat flow along desired paths. Aheatsink can have an arbitrary shape, optimized for thermal and end-useconsiderations. The heatsink for a cylindrical-shaped lamp body mightalso be cylindrical with fins and mounting details standardized forattachment to a projection television chassis, and with features formounting optics to the lamp assembly. For a cylindrical lamp andcylindrical heatsink, a useful construction technique is to heat theheatsink until it expands, then place it around the lamp body, and letit cool and contract to form intimate mechanical contact with the body.A metallic heatsink can be used to provide a conductive outer coating ofthe lamp body. This technique ensures a durable and intimate connection,and satisfies both thermal and electrical requirements of the lamp,reducing its total cost.

Referring to FIG. 4, a DWIPL 400 includes a generally cylindrical lampbody 402 having a top face 404 with a surface 404S to which is attacheda window 406 covering a lamp chamber aperture 408. Body 402 is closelyreceived within a generally cylindrical bore 410 of a generallycylindrical metallic heatsink 412 having an annular upper face 414 witha plurality of mounting holes 416. Preferably, a compliant, hightemperature thermal interface material 418, e.g., grease or a siliconepad, is inserted between body 402 and heatsink 412.

Another practical heatsink arrangement is a two-piece “clamshell” inwhich two similar or identical pieces make intimate contact with a lampbody over a large area. The pieces are held together by fasteners incompression. Referring to FIG. 5, a DWIPL 500 has a generallycylindrical body 502, a top face 504 with a surface 504S, and a window506 attached to surface 504S and covering a lamp chamber aperture 508.Body 502 is enclosed by semi-cylindrical portions 510, 512 of aclamshell-type heatsink 514. Portions 510 and 512 each are determined byends 510A, 510B and 512A, 512B, respectively, attached to flanges 510C,510D and 512C, 512D, respectively. First and second fasteners 520, 522are used to connect the aligned flanges, compressing portions 510, 512about the body 502.

Still another heatsink arrangement is to plate a lamp body with athermally and electrically conductive material, such as silver ornickel, and then solder or braze heatsink pieces to the plating.

When microwave power is applied from the driver circuit to the lampbody, it heats the fill mixture, melting and then vaporizing the salt orhalide, causing a large increase in the lamp chamber pressure. Dependingon the salt or halide used, this pressure can become as high as 400atmospheres, and the bulb temperature can be as high as 1000° C.Consequently, a seal attaching a window or lens to a lamp body must beextremely robust.

Referring to FIG. 6, a DWIPL 600 includes a body 602 having a side 604with a surface 604S from which depends a lamp chamber 606 having anaperture 608 and a bottom 610 with a hole 610H. A window 612, preferablymade of sapphire, is attached to surface 604S by a seal 614. Lamp body602 further includes a tapped bore 616 extending between a hole 620H ina body side 618 generally opposed to side 604, and chamber bottom 610,so that the bore is in communication with hole 610H. The window 612 issealed to surface 604S in an inert atmosphere, using a ceramic sealingtechnique known in the art, such as brazing, frit, or metal sealing.Lamp body 602 and a screw-type plug 620 having a head 622 are thenbrought into an atmospheric chamber containing the starting gas 607G tobe used in the lamp chamber, which is at or near the desirednon-operating pressure for the lamp. The light emitter 607E is thendeposited in lamp chamber 606 through bore 616 and hole 610H. Plug 620,which provides a mechanical and gas barrier to contain the fill mixture,is then screwed into bore 616 through hole 620H, and a metallic or glassmaterial 624 deposited over head 622 to effect a final seal.

Referring to FIGS. 7 and 7A, a DWIPL 700 includes a body 702 having aside 704 with a surface 704S from which depends a lamp chamber 706having a first aperture 708 and a lower portion 710 tapering in a neck712 terminating in a second aperture 714. A window 716, preferably madeof sapphire, is attached to surface 704S by a seal 718. Lamp body 702further includes a tapered bore 720 extending between a hole 720H in abody side 722 generally opposed to side 704, and aperture 714, so thatthe bore is in communication with the neck 712, forming a lip 713.Window 716 is sealed to surface 704S in an inert atmosphere. Lamp body702 and a plug 730, tapered to match the taper of bore 720 and having ahead 732, are then brought into an atmospheric chamber containing thestarting gas 707G to be used in the lamp chamber, which is at or nearthe desired non-operating pressure for the lamp. The light emitter 707Eis then deposited in lamp chamber 706 through bore 720 and aperture 714.Plug 730 is then force-fitted through hole 720H into bore 720 so thatthe plug contacts lip 713, effecting a mechanical seal, and a metallicor glass material 734 deposited over head 732 to effect a final seal.

FIG. 8 shows three configurations 630, 640, 650 of the screw-type plug620, and four configurations 740, 750, 760, 770 of the tapered plug 730.Plugs 630, 640 and 650 have, respectively, a dome-shaped tip 630T, arod-shaped tip 640T, and a chisel-shaped tip 650T. Plugs 740, 750, 760and 770 have, respectively, a conical tip 740T, a cup-shaped tip 750T, achisel-shaped tip 760T, and a rod-shaped tip 770T having a concave end722. If a plug having an extended tip such as plug 650 or plug 760 isused, the tip extends well into chamber 706 creating a discontinuitywhich provides an electric field concentration point.

Referring to FIG. 9, a DWIPL 900 includes a body 902 having a side 904with a surface 904S from which depends a lamp chamber 906 having anaperture 908 and a bottom 910 with a hole 910H. A window 912, preferablymade of sapphire, is attached to surface 904S by a seal 914. Lamp body902 further includes a cylindrical bore 916 extending between a bodyside 918 generally opposed to side 904, and chamber bottom 910, so thatthe bore is in communication with hole 910H. After window 912 is sealedto surface 904S in an inert atmosphere, a glass or quartz tube 920having an end 920E is inserted into bore 916 through a hole 916H so thatend 920E extends through hole 910H into chamber 906. The chamber is thenevacuated by a vacuum pump connected to tube 920. A fill mixture ofstarting gas 907G and light emitter 907E is then deposited into thechamber via the tube. When the fill is complete, a glass or quartz rod930 having an outer diameter a little smaller than the inner diameter ofthe tube is inserted into the tube, and the tube and rod heated andpinched off. Thus, tube 920 is filled with a dielectric material whichprovides a reliable seal. The chamber filling and sealing process can bedone without resort to a vacuum chamber, i.e., with the lamp atatmospheric pressure. Alternatively, the lamp body 902 with tube 920inserted into bore 916 is brought into an atmospheric chamber containingthe starting gas to be used in the lamp chamber, which is at or near thedesired non-operating pressure for the lamp. The light emitter is thenintroduced into the chamber via the tube. When the fill is complete, therod 930 is inserted into the tube, and the tube and rod heated andpinched off.

Referring to FIG. 10, a DWIPL 1000 includes a body 1002 having a side1004 with a surface 1004S from which depends a lamp chamber 1006 havingan aperture 1008 and a bottom 1010. Side 1004 has a hole 1004H incommunication with a hole 1006H in chamber 1006. A glass or quartz tube1020 having an end 1020E is inserted through holes 1004H and 1006H sothat the end penetrates the chamber. A window 1030 covering aperture1008, preferably made of sapphire, is then attached to surface 1004S bya frit or sealing material 1032 which melts at a temperature which willnot melt the tube. After the window is sealed to surface 1004S with thetube 1020 in place and hole 1004H plugged by the sealing material, thechamber is evacuated by a vacuum pump connected to the tube. A fillmixture of starting gas 1007G and light emitter 1007E is then depositedinto the chamber via the tube. When the fill is complete, a glass orquartz rod 1040 with an outer diameter a little smaller than the innerdiameter of tube 1020 is inserted into the tube, and the tube 1020 androd 1040 heated and pinched off.

Referring to FIG. 11, a DWIPL 1100 includes a body 1102 having a side1104 with a surface 1104S from which depends a lamp chamber 1106 havingan aperture 1108 and a bottom 1110. Side 1104 has an O-ring groove 1112circumscribing the aperture 1108. DWIPL 1100 further includes first andsecond clamps 1120A, 1120B, respectively, which can apply mechanicalcompression to a window 1130 covering the aperture. The lamp body 1102,window 1130, an O-ring 1114, and a fill mixture of starting gas 1140 andlight emitter 1150 are brought into an atmospheric chamber containingthe gas 1140 at a pressure at or near the desired non-operating pressurefor the lamp. The light emitter is then deposited in the chamber 1106,the O-ring 1114 is placed into groove 1112, the window 1130 is placed ontop of the O-ring, and the clamps 1120A, 1120B tightened, thus forming atemporary or permanent seal.

Referring to FIG. 12, a DWIPL 1200 includes a “U”-shaped body 1202having a central body portion 1204 attached to generally opposed firstand second body portions 1206, 1208, respectively, which are generallyorthogonal to body portion 1204 and extend in upper portions 1206U,1208U, respectively. Body portion 1204 has a side 1210 with a surface1210S from which depends a lamp chamber 1220 having an aperture 1222 anda bottom 1224. Side 1210 has an O-ring groove 1212 which circumscribesaperture 1222. Upper portions 1206U, 1208U have, respectively, aninterior surface 1206S, 1208S, having a thread 1230. The thread may be ametallic attachment to the interior surfaces or cut into the surfaces.As for the FIG. 11 embodiment, the lamp body 1202 and a window 1240, anO-ring 1214, and a fill mixture of starting gas 1221G and light emitter1221E are brought into an atmospheric chamber containing the gas at apressure at or near the desired non-operating pressure for the lamp. Thelight emitter is deposited in the chamber 1220, the O-ring 1214 isplaced into groove 1212, the window 1240 is placed on top of the O-ring,and a screw-type metallic cap 1250 is engaged with the thread 1230. Cap1250 has therethrough a central hole 1250H which serves as a lighttunnel. Screwing down the cap applies pressure to the window, therebycompressing the O-ring to form a temporary or permanent seal.

Referring to FIG. 13, a DWIPL 1300 includes a body 1302 having a side1304 with a surface 1304S from which depends a lamp chamber 1306 havingan aperture 1308 and a bottom 1310. Side 1304 has therein a detail 1312circumscribing the aperture 1308 and adapted to closely receive a sealpreform 1320, such as a platinum or glass ring. The lamp body 1302, awindow 1330, the seal 1320, and a fill mixture of starting gas 1340 andlight emitter 1350 are brought into an atmospheric chamber containingthe gas 1340 at a pressure at or near the desired non-operating pressurefor the lamp. The light emitter is deposited in the chamber 1306, theseal 1320 placed in the detail 1312, and the window 1330 placed on topof the seal preform. The lamp body 1302 is then placed on or clamped toa cold surface 1360, so that the body and fill mixture remainsufficiently cool that no materials vaporize during heating of the sealpreform. A hot mandrel 1370 is then applied in pressing contact towindow 1330, heating the window and melting the seal preform. Indicia1370A and 1370B denote melt-through heat transfer. The seal preformmaterial is chosen to melt and flow at a temperature below the thermallimit for the window and lamp body. When the seal preform melts and thenis cooled, it forms a seal between the window and side 1304. During thesealing operation, the gas pressure in the lamp chamber must be selectedto compensate for expansion during heating.

Referring to FIG. 14, a DWIPL 1400 includes a body 1402 having a side1404 with a surface 1404S from which depends a lamp chamber 1406 havingan aperture 1408 and a bottom 1410. Attached to side 1404 by brazing,vacuum deposition or screening, and disposed within a detail 1404D inside 1404 is a first metallization ring 1412 circumscribing the aperture1408. Within detail 1404D is a seal preform 1420, such as a platinumring, superposed on ring 1412. A window 1430 has a lower surface 1430Sto which, proximate to its periphery, is attached by brazing, vacuumdeposition or screening a second metallization ring 1432. The lamp body1402, the window 1430, the seal preform 1420, and a fill mixture ofstarting gas 1440 and light emitter 1450 are brought into an atmosphericchamber containing the gas 1440 at a pressure at or near the desirednon-operating pressure for the lamp. The light emitter is deposited inthe chamber 1406, and the window 1430 placed on top of the seal preform1420 so that the preform is sandwiched between rings 1412 and 1432.Preferably, a clamp 1460 holds the window in place while a brazing flame1470 or other heat source is applied to melt the preform and form aseal.

Referring to FIG. 15, a DWIPL 1500 includes a body 1502 having a side1504 with a surface 1504S from which depends a lamp chamber 1506 havingan aperture 1508 and a bottom 1510. Attached to side 1504 by brazing,vacuum deposition or screening, and disposed within a detail 1504D inside 1504 is a first metallization ring 1512 circumscribing the aperture1508. Within detail 1504D is a seal preform 1520, such as a platinum orglass ring, superposed on ring 1512. A window 1530 has a lower surface1530S to which, proximate to its periphery, is attached by brazing,vacuum deposition or screening a second metallization ring 1532. Thelamp body 1502, the window 1530, the seal preform 1520, and a fillmixture of starting gas 1540 and light emitter 1550 are brought into anatmospheric chamber containing the gas 1540 at a pressure at or near thedesired non-operating pressure for the lamp. The mixture is deposited inthe chamber 1506, and the window 1530 placed on top of the seal preform1520 so that the preform is sandwiched between rings 1512 and 1532.Preferably, a clamp 1560 holds the window in place while a laser 1570 isfocused and moved in a controlled pattern to melt and then permitcooling of the seal preform material. Laser sealing can be done atatmospheric or partial pressure.

Referring to FIGS. 16 and 16A, a DWIPL 1600 includes a body 1602 havinga side 1604 with a surface 1604S from which depends a lamp chamber 1606having an aperture 1608 and a bottom 1610. Attached to side 1604 bybrazing, vacuum deposition or screening, and disposed within a detail1604D of side 1604 is a first metallization ring 1612 circumscribing theaperture 1608. Within detail 1604D is a seal preform 1620, such as aplatinum or other conductive material, superposed on ring 1612. A window1630 has a lower surface 1630S to which, proximate to its periphery, isattached by brazing, vacuum deposition or screening a secondmetallization ring 1632. The lamp body 1602, the window 1630, the sealpreform 1620, and a fill mixture of starting gas 1640 and light emitter1650 are brought into an atmospheric chamber containing the gas 1640 ata pressure at or near the desired non-operating pressure for the lamp.The light emitter 1650 is deposited in the chamber 1606, and the window1630 placed on top of the seal preform 1620 so that the preform issandwiched between rings 1612 and 1632. Preferably, a clamp 1660 holdsthe window in place while a radio frequency (RF) coil 1670 is movedclose to the seal preform. The coil heats and melts the preform which,after cooling, forms a seal between the window and side 1604. RF sealingcan be done at atmospheric or partial pressure.

Electromagnetically, a DWIPL is a resonant cavity having at least onedrive probe supplying microwave power for energizing a plasma containedin at least one bulb. In the following portion of the detaileddescription “cavity” denotes a DWIPL body. As disclosed in the '718application, a “bulb” may be a separate enclosure containing a fillmixture disposed within a lamp chamber, or the chamber itself may be thebulb. To provide optimal efficiency, a bulb preferably is located at anelectric field maximum of the resonant cavity mode being used. Howeverthe bulb can be moved away from a field maximum at the cost ofadditional power dissipated by the wall and cavity. The location of thedrive probe is not critical, as long as it is not at a field minimum,because the desired coupling efficiency can be achieved by varying probedesign parameters, particularly length and shape. FIGS. 17A and 17Bschematically show two cylindrical lamp configurations 130A, 130B,respectively, both operating at the fundamental cylindrical cavity mode,commonly known as TM_(0,1,0), and having a bulb 132A, 132B,respectively, located at the single electric field maximum. Dashedcurves 131A, 131B show, respectively, the electric field distribution inthe cavity. In FIG. 17A, a drive probe 134A is located at the fieldmaximum. In FIG. 17B, drive probe 134B is not located at the fieldmaximum; however, it contains a longer probe which provides the samecoupling efficiency as probe 134A. Although the TM_(0,1,0) mode is usedhere as an example, higher order cavity modes, including but not limitedto transverse electric field (“TE”) and transverse magnetic field (“TM”)modes, can also be used.

Drive probe design is critical for proper lamp operation. The probe mustprovide the correct amount of coupling between the microwave source andlamp chamber to maximize light emitting efficiency and protect thesource. There are four major cavity loss mechanisms reducing efficiency:chamber wall dissipation, dielectric body dissipation, plasmadissipation, and probe coupling loss. As defined herein, probe couplingloss is the power coupled out by the drive probe and other probes in thecavity. Probe coupling loss is a major design consideration because anyprobe can couple power both into and out of the cavity. If the couplingbetween the source and cavity is too small, commonly known as“under-coupling”, much of the power coming from the source will notenter the cavity but be reflected back to the source. This will reducelight emission efficiency and microwave source lifetime. If initiallythe coupling between the source and cavity is too large, commonly knownas “over-coupling”, most of the power from the source will enter thecavity. However, the cavity loss mechanisms will not be able to consumeall of the power and the excess will be coupled out by the drive probeand other probes in the cavity. Again, light emission efficiency andmicrowave source lifetime will be reduced. In order to maximize lightemission efficiency and protect the source, the drive probe must providean appropriate amount of coupling such that reflection from the cavityback to the source is minimized at the resonant frequency. Thiscondition, commonly known as “critical coupling”, can be achieved byadjusting the configuration and location of the drive probe. Probedesign parameters depend on the losses in the cavity, which depend onthe state of the plasma and the temperature of the lamp body. As theplasma state and/or body temperature change, the coupling and resonantfrequency will also change. Moreover, inevitable inaccuracies duringDWIPL manufacture will cause increased uncertainty in the coupling andresonant frequency.

It is not practical to adjust probe physical parameters while a lamp isoperating. In order to maintain as close to critical coupling aspossible under all conditions, a feedback configuration is required (seeFIG. 6 of the '718 application), such as lamp configurations 140A, 140Bshown, respectively, in FIGS. 18A and 18B for a rectangular prism-shapedcavity and a cylindrical cavity. A second “feedback” probe 142A, 142B,respectively, is introduced into a cavity 144A, 144B, respectively.Feedback probe 142A, 142B, respectively, is connected to input port146A, 146B, respectively, of a combined amplifier and control circuit(ACC) 148A, 148B, respectively, and a drive probe 150A, 150B,respectively, is connected to ACC output port 152A, 152B, respectively.Each configuration forms an oscillator. Resonance in the cavity enhancesthe electric field strength needed to create the plasma and increasesthe coupling efficiency between the drive probe and bulb. Both the driveprobe and feedback probe may be located anywhere in the cavity exceptnear an electric field minimum for electric field coupling, or amagnetic field minimum for magnetic field coupling. Generally, thefeedback probe has a lesser amount of coupling than the drive probebecause it samples the electric field in the cavity with minimumincrease in coupling loss.

From a circuit perspective, a cavity behaves as a lossy narrow bandpassfilter. The cavity selects its resonant frequency to pass from thefeedback probe to the drive probe. The ACC amplifies this preferredfrequency and puts it back into the cavity. If the amplifier gain isgreater than the insertion loss at the drive probe entry port vis-a-visinsertion loss at the feedback probe entry port, commonly known as S₂₁,oscillation will start at the resonant frequency. This is doneautomatically and continuously even when conditions, such as plasmastate and temperature, change continuously or discontinuously. Feedbackenables manufacturing tolerances to be relaxed because the cavitycontinually “informs” the amplifier of the preferred frequency, soaccurate prediction of eventual operating frequency is not needed foramplifier design or DWIPL manufacture. All the amplifier needs toprovide is sufficient gain in the general frequency band in which thelamp is operating. This design ensures that the amplifier will delivermaximum power to the bulb under all conditions.

In order to maximize light emission efficiency, a drive probe isoptimized for a plasma that has reached its steady state operatingpoint. This means that prior to plasma formation, when losses in acavity are low, the cavity is over-coupled. Therefore, a portion of thepower coming from the microwave source does not enter the cavity and isreflected back to the source. The amount of reflected power depends onthe loss difference before and after plasma formation. If thisdifference is small, the power reflection before plasma formation willbe small and the cavity will be near critical coupling. Feedbackconfigurations such as shown in FIG. 18A or 18B will be sufficient tobreak down the gas in the bulb and start the plasma formation process.However, in most cases the loss difference before and after plasmaformation is significant and the drive probe becomes greatlyover-coupled prior to plasma formation. Because much of the power isreflected back to the amplifier, the electric field strength may not belarge enough to cause gas breakdown. Also, the large amount of reflectedpower may damage the amplifier or reduce its lifetime.

FIG. 19 shows a lamp configuration 160 which solves the drive probeover-coupling problem wherein a third “start” probe 162, optimized forcritical coupling before plasma formation, is inserted into a cavity164. Start probe 162, drive probe 166, and feedback probe 168 can belocated anywhere in the cavity except near a field minimum. Power fromoutput port 170B of an ACC 170 is split into two portions by a splitter172: one portion is delivered to drive probe 166; the other portion isdelivered to start probe 162 through a phase shifter 174. Probe 168 isconnected to input port 170A of ACC 170. Both the start and drive probesare designed to couple power into the same cavity mode, e.g., TM_(0,1,0)for a cylindrical cavity as shown in FIG. 19. The splitting ratio andamount of phase shift between probes 166 and 162 are selected tominimize reflection back to the amplifier. Values for these parametersare determined by network analyzer S-parameter measurements and/orsimulation software such as High Frequency Structure Simulator (HFSS)available from Ansoft Corporation of Pittsburgh, Pa. In summary, thestart probe is critically coupled before plasma formation and the driveprobe is critically coupled when the plasma reaches steady state. Thesplitter and phase shifter are designed to minimize reflection back tothe combined amplifier and control circuit.

FIG. 20 shows a second lamp configuration 180 which solves the driveprobe over-coupling problem. Both start probe 182 and drive probe 184are designed to couple power into the same cavity mode, e.g., TM_(0,1,0)for a cylindrical cavity such as cavity 186. Configuration 180 furtherincludes a feedback probe 188 connected to input port 190A of an ACC190. The three probes can be located anywhere in the cavity except neara field minimum. Power from output port 190B of ACC 190 is delivered toa first port 192A of a circulator 192 which directs power from port 192Ato a second port 192B which feeds drive probe 184. Prior to plasmaformation, there is a significant amount of reflection coming out of thedrive probe because it is over-coupled before the plasma reaches steadystate. Such reflection is redirected by circulator 192 to a third port192C which feeds the start probe 182. Before plasma formation, the startprobe is critically coupled so that most of the power is delivered intothe cavity 186 and start probe reflection is minimized. Only aninsignificant amount of power goes into port 192C and travels back toACC output port 190B. Power in the cavity increases until the fillmixture breaks down and begins forming a plasma. Once the plasma reachessteady state, the drive probe 184 is critically coupled so reflectionfrom the drive probe is minimized. At that time, only an insignificantamount of power reaches the now under-coupled start probe 182. Althoughthe start probe now has a high reflection coefficient, the total amountof reflected power is negligible because the incident power isinsignificant. In summary, the start probe is critically coupled beforeplasma formation and the drive probe is critically coupled when theplasma reaches steady state. The circulator directs power from port 192Ato 192B, from port 192B to port 192C, and from port 192C to port 192A.

FIGS. 21A and 21B show third and fourth lamp configurations 240A, 240Bwhich solve the drive probe over-coupling problem. A “start” cavity modeis used before plasma formation, and a separate “drive” cavity mode isused to power the plasma to its steady state and maintain that state.Start probe 242A, 242B, respectively, operates in the start cavity mode,and drive probe 244A, 244B, respectively, operates in the drive cavitymode. As indicated by dashed curves 241A and 241B, preferably the drivecavity mode is the fundamental cavity mode and the start cavity mode isa higher order cavity mode. This is because normally it requires morepower to maintain the steady state plasma with the desired light outputthan to break down the gas for plasma formation. Therefore it is moreeconomical to design a DWIPL so the high power microwave source operatesat a lower frequency. For a cylindrical cavity such as cavities 246A and246B, the start probe 242A, 242B, respectively, can be criticallycoupled at the resonant frequency of the TM_(0,2,0) mode before plasmaformation, and the drive probe 244A, 244B, respectively, can be coupledat the resonant frequency of the TM_(0,1,0) mode after the plasmareaches steady state. The feedback probe can be located anywhere in thecavity except near a field minimum of the drive cavity mode or a fieldminimum of the start cavity mode. The start probe can be locatedanywhere in the cavity except near any field minima of the start cavitymode. The drive probe should be located near or at a field minimum ofthe start cavity mode but not near a field minimum of the drive cavitymode. This minimizes the coupling loss of the drive probe before plasmaformation so that the electric field in the cavity can reach a highervalue to break down the gas. A diplexer 248A, 248B, respectively, isused to separate the two resonant frequencies. In FIG. 21A, a single ACC250 connected at its input 250B to diplexer 248A is used to power bothcavity modes. The two frequencies are separated by diplexer 248A and fedto the start probe 242A and drive probe 244A. Feedback probe 252A isconnected to input port 250A of ACC 250. In FIG. 21B, two separateamplifiers 260, 262 are used to power the two cavity modesindependently. Diplexer 248B separates the two frequencies coming out offeedback probe 252B. In summary, the start probe operates in one cavitymode and the drive probe operates in a different mode. The feedbackprobe can be located anywhere in the cavity except near a field minimumof either mode. The start probe can be located anywhere in the cavityexcept near a field minimum of the start cavity mode. The drive probeshould be located near or at a field minimum of the start cavity modebut not near a field minimum of the drive cavity mode.

An alternative approach is to add a second feedback probe, whicheliminates the need for a diplexer. The first feedback probe is locatedat a field minimum of the start cavity mode to couple out only the drivecavity mode. The second feedback probe is located at a field minimum ofthe drive cavity mode to couple out only the start cavity mode.

FIGS. 22A and 22B show lamp configurations 280A, 280B, respectively,which do not include a start probe but utilize two separate cavitymodes. As indicated by curves 281A and 281B, respectively, in cavities282A and 282B, a relatively high order start cavity mode is used beforeplasma formation and a relatively low order drive cavity mode is used topower the plasma to steady state and maintain the state. Preferably, foreconomy and efficiency, the drive cavity mode again is the fundamentalcavity mode and the start cavity mode is a higher order cavity mode. Forexample, the TM_(0,2,0) mode of a cylindrical lamp cavity can be usedbefore plasma formation, and the TM_(0,1,0) mode can be used to maintainthe plasma in steady state. By utilizing two cavity modes, it ispossible to design a single drive probe that is critically coupled bothbefore plasma formation and after the plasma reaches steady state,thereby eliminating the need for a start probe. The feedback probe 284A,284B, respectively, can be located anywhere in the cavity except near afield minimum of either cavity mode. The drive probe 286A, 286B,respectively, should be located near a field minimum of the start cavitymode but not near a field minimum of the drive cavity mode. By placingthe drive probe near but not at a field minimum of the start cavitymode, the drive probe can be designed to provide the small amount ofcoupling needed before plasma formation and the large amount of couplingrequired after the plasma reaches steady state. In FIG. 22A, a singleACC 290 having input and output ports 290A, 290B, respectively, is usedto power both cavity modes. In FIG. 22B, two separate ACC's 292, 294 areused to power the two cavity modes independently. A first diplexer 296Bseparates the two frequencies coming out of feedback probe 284B and asecond diplexer 298B combines the two frequencies going into drive probe286B. In summary, the drive probe is critically coupled at the startcavity mode resonant frequency before plasma formation and criticallycoupled at the drive cavity mode resonant frequency when the plasmareaches steady state. The feedback probe can be located anywhere in thecavity except near a field minimum of either cavity mode. The driveprobe should be located near a field minimum of the start cavity modebut not near a field minimum of the drive cavity mode.

The '718 application disclosed a technique for drive probe constructionwherein a metallic microwave probe is in intimate contact with the highdielectric material of the lamp body. This method has a drawback in thatthe amount of coupling is very sensitive to the exact dimensions of theprobe. A further drawback is that due to the large temperature variationbefore plasma formation and after the plasma reaches steady state, amechanism such as a spring is needed to maintain contact between theprobe and body. These constraints complicate the manufacturing processand consequently increase production cost.

FIG. 23 shows a technique which avoids both problems. A metallicmicrowave probe 350 extending into a lamp body 352 is surrounded by adielectric material 354 having a high breakdown voltage. Body 352includes a lamp chamber 356. Due to the large amount of power deliveredwithin a limited space, the electric field strength near tip 350T ofprobe 350 is very high; therefore a high breakdown voltage material isrequired. Typically, material 354 has a lower dielectric constant thanthat of the dielectric material forming body 352. Material 354 acts as a“buffer” which desensitizes the dependency of coupling on probedimensions, thereby simplifying fabrication and reducing cost.

The amount of coupling between the microwave source and body can beadjusted by varying the location and dimensions of the probe, and thedielectric constant of material 354. In general, if the probe length isless than a quarter of the operating wavelength, a longer probe willprovide greater coupling than a shorter probe. Also, a probe placed at alocation with a higher field will provide greater coupling than a probeplaced at a location where the field is relatively low. This techniqueis also applicable to a start probe or a feedback probe. The probelocation, shape and dimensions can be determined using network analyzerS-parameter measurements and/or simulation software such as HFSS.

FIG. 24 shows a circuit 430 including an amplifier 432 and a controlcircuit 434, suitable for DWIPLs having only a drive probe 436 andfeedback probe 438 such as shown in FIGS. 18A, 18B, 22A and 22B, andexemplified here by lamp 420. The function of amplifier 432 is toconvert DC power into microwave power of an appropriate frequency andpower level so that sufficient power can be coupled into lamp body 440and lamp chamber 442 to energize a fill mixture and form alight-emitting plasma.

Preferably, amplifier 432 includes a preamplifier stage 450 with 20 to30 dBm of gain, a medium power amplifier stage 452 with 10 to 20 dB ofgain, and a high power amplifier stage 454 with 10 to 18 dB of gain.Preferably, stage 450 uses the Motorola MHL21336, 3G Band RF LinearLDMOS Amplifier, stage 452 uses the Motorola MRF21030 Lateral N-ChannelRF Power MOSFET; and stage 454 uses the Motorola MRF21125 LateralN-Channel RF Power MOSFET. These devices as well as complete informationfor support and bias circuits are available from Motorola SemiconductorProducts Sector in Austin, Tex. Alternatively, stages 450, 452 and 454are contained in a single integrated circuit. Alternatively, stages 450and 452, and control circuit 434 are packaged together, and high powerstage 454 is packaged separately.

Amplifier 432 further includes a PIN diode attenuator 460 in series withstages 450, 452 and 454, preferably connected to preamplifier stage 450to limit the amount of power which the attenuator must handle.Attenuator 460 provides power control for regulating the amount of powersupplied to lamp body 440 appropriate for starting the lamp, operatingthe lamp, and controlling lamp brightness. Since the amplifier chainformed by stages 450, 452 and 454 has a fixed gain, varying theattenuation during lamp operation varies the power delivered to body440. Preferably, the attenuator 460 acts in combination with controlcircuit 434, which may be analog or digital, and an optical powerdetector 462 which monitors the intensity of the light emitted andcontrols attenuator 460 to maintain a desired illumination level duringlamp operation, even if power conditions and/or lamp emissioncharacteristics change over time. Alternatively, an RF power detector464 connected to drive probe 436, amplifier stage 454 and controlcircuit 434 is used to control the attenuator 460. Additionally, circuit434 can be used to control brightness, i.e., controlling the lampillumination level to meet end-application requirements. Circuit 434includes protection circuits and connects to appropriate sensingcircuits to provide the functions of over-temperature shutdown,over-current shutdown, and over-voltage shutdown. Circuit 434 can alsoprovide a low power mode in which the plasma is maintained at a very lowpower level, insufficient for light emission but sufficient to keep thefill mixture gas ionized. Circuit 434 also can shut down the lamp slowlyby increasing the attenuation. This feature limits the thermal shock alamp repeatedly experiences and allows the fill mixture to condense inthe coolest portion of the lamp chamber, promoting easier lamp starting.

Alternatively, attenuator 460 is combined with an analog or digitalcontrol circuit to control the output power at a high level during theearly part of the lamp operating cycle, in order to vaporize the fillmixture more quickly than can be achieved at normal operating power.Alternatively, attenuator 460 is combined with an analog or digitalcontrol circuit which monitors transmitted and/or reflected microwavepower levels through an RF power detector and controls the attenuator tomaintain the desired power level during normal lamp operation, even ifthe incoming power supply voltage changes due to variations in the acsupply or other loads.

FIG. 25 shows an alternative circuit 540 including an amplifier 542 anda control circuit 544, suitable for supplying and controlling power tothe body 546 and lamp chamber 548 of a DWIPL 550 having a drive probe552 and feedback probe 554, such as shown in FIGS. 18A, 18B, 22A and22B. A “starting” bandpass filter 560A and an “operating” bandpassfilter 560B, in parallel and independently selectable and switchable,are in series with the FIG. 24 amplifier chain and preferably, as inFIG. 24, on the input side of the chain. Filters 560A and 560B filterout frequencies corresponding to undesired resonance modes of body 546.By selecting and switching into the circuit a suitable filter bandpassusing first and second PIN diode switches 562A, 562B, the DWIPL 550 canoperate only in the cavity mode corresponding to the selected frequencyband, so that all of the amplifier power is directed into this mode. Byswitching in filter 560A, a preselected first cavity mode is enabled forstarting the lamp. Once the fill mixture gas has ionized and the plasmabegun to form, a preselected second cavity mode is enabled by switchingin filter 560B. For a short time, both filters provide power to the lampto ensure that the fill mixture remains a plasma. During the period whenboth filters are switched in, both cavity modes propagate through body546 and the amplifier chain. When a predetermined condition has beenmet, such as a fixed time delay or a minimum power level, filter 560A isswitched out, so that only the cavity mode for lamp operation canpropagate through the amplifier chain. Control circuit 544 selects,deselects, switches in, and switches out filters 560A and 560B,following a predetermined operating sequence. An optical power detector564 connected to control circuit 544 performs the same function asdetector 462 in the FIG. 24 embodiment.

FIG. 26 shows a circuit 570 including an amplifier 572 and an analog ordigital control circuit 574, suitable for supplying and controllingpower to the body 576 and lamp chamber 578 of a DWIPL 580 having a driveprobe 582, a feedback probe 586 and a start probe 584, such as shown inFIGS. 19, 20, 21A and 21B. The feedback probe 586 is connected to input450A of preamplifier 450 through a PIN diode attenuator 588 and a filter589. The start probe 584 is designed to be critically coupled when lamp580 is off. To start the lamp, a small amount of microwave power isdirected into start probe 584 from preamplifier stage 450 or mediumpower stage 452 of the amplifier chain. The power is routed through abipolar PIN diode switch 590 controlled by control circuit 574. Switch590 is controlled to send RF microwave power to start probe 584 untilthe fill mixture gas becomes ionized. A sensor 592A monitors power usagewithin body 576, and/or a sensor 592B monitors light intensityindicative of gas ionization. A separate timer control circuit, which ispart of control circuit 574, allocates an adequate time for gasbreakdown. Once the gas has been ionized, control circuit 574 turns onswitch 590 which routes microwave power to high power stage 454 whichprovides microwave power to drive probe 582. For a short time, startprobe 584 and drive probe 582 both provide power to the lamp to ensurethat the fill mixture remains a plasma. When a predetermined conditionhas been met, such as a fixed time period or an expected power level,control circuit 574 turns off switch 590 thereby removing power to startprobe 584 so that the plasma is powered only by drive probe 582. Thisprovides maximum efficiency.

To enhance the Q-value (i.e., the ratio of the operating frequency tothe resonant frequency bandwidth) of the DWIPL 580 during starting, thecontrol circuit 574 can bias the transistors of high power stage 454 toan impedance that minimizes leakage out of probe 582 into stage 454. Toaccomplish this, circuit 574 applies a DC voltage to the gates of thetransistors to control them to the appropriate starting impedance.

1. A lamp comprising: (a) a waveguide having a body of a preselectedshape and preselected dimensions consisting essentially of at least onesolid dielectric material, the body having a first side determined by afirst waveguide outer surface; (b) a lamp chamber depending from saidfirst side and having an aperture at said waveguide outer surfacegenerally opposed to a lamp chamber bottom, the waveguide body and lampchamber comprising an integrated structure; (c) the waveguide bodycoupled to a source of microwave power having an output and an input andoperating at a preselected frequency and intensity, said frequency andintensity and said body shape and dimensions selected such that thewaveguide body resonates in at least one resonant mode having at leastone electric field maximum; and (d) the lamp chamber containing a fillmixture consisting essentially of a starting gas and a light emitter,the fill mixture when receiving microwave power at said frequency andintensity, provided by the resonating waveguide body, forming a plasmawhich emits light.
 2. The lamp of claim 1, further comprising: means fordepositing the starting gas and light emitter within the lamp chamber;and means for sealing the aperture to the external environment, therebysealing the lamp chamber to said environment while allowing transmissionof light from the lamp chamber.
 3. The lamp of claim 1, furthercomprising a self-enclosed bulb disposed within the lamp chamber andcontaining said fill mixture.
 4. The lamp of claim 2 or 3, furthercomprising a first (“drive”) probe and a second (“feedback”) probedisposed within said waveguide body anywhere except near a minimum ofthe electric field resulting from the source operating at a frequencysuch that the waveguide body resonates in a single resonant mode, thefirst probe connected to said source output and the second probeconnected to said source input, thereby forming an oscillatorconfiguration maintaining the first probe such that power reflected fromthe waveguide body back to the source is minimized.
 5. The lamp of claim2 or 3, further comprising a first (“drive”) probe and a second(“feedback”) probe disposed within said waveguide body, the sourceoperating at a first frequency such that the waveguide body resonates ina relatively higher order resonant mode before the plasma is formed, andat a second frequency such that the waveguide body resonates in arelatively lower order resonant mode after the plasma reaches a steadystate, the first probe disposed near an electric field minimum of thehigher order mode and not near an electric field minimum of the lowerorder mode, the second probe disposed anywhere except near an electricfield minimum of the higher order mode or the lower order mode, thefirst probe connected to said source output and the second probeconnected to said source input, thereby forming an oscillatorconfiguration maintaining the first probe such that power reflected fromthe waveguide body back to the source is minimized both before theplasma is formed and after the plasma reaches said steady state.
 6. Thelamp of claim 2 or 3, further comprising a first (“drive”) probe, asecond (“feedback”) probe, and a third (“start”) probe disposed withinsaid waveguide body anywhere except near a minimum of the electric fieldresulting from the source operating at a frequency such that thewaveguide body resonates in a single resonant mode, the first probeconnected to said source output, the second probe connected to saidsource input, and the third probe connected to said source outputthrough a phase shifter and a splitter, thereby forming a configurationmaintaining the third probe such that power reflected from the waveguidebody back to the source is minimized before the plasma is formed, andmaintaining the first probe such that power reflected from the waveguidebody back to the source is minimized after the plasma reaches a steadystate.
 7. The lamp of claim 2 or 3, further comprising: a first(“drive”) probe, a second (“feedback”) probe, and a third (“start”)probe disposed within said waveguide body anywhere except near a minimumof the electric field resulting from the source operating at a frequencysuch that the waveguide body resonates in a single resonant mode; and acirculator having interconnected first, second and third ports, thefirst probe connected to said second port, said first port connected tosaid source output, the second probe connected to said source input, andsaid third port connected to the third probe, thereby forming aconfiguration maintaining the third probe such that power reflected fromthe waveguide body back to the source is minimized before the plasma isformed, and maintaining the first probe such that power reflected fromthe waveguide body back to the source is minimized after the plasmareaches a steady state.
 8. The lamp of claim 2 or 3, further comprisinga first (“drive”) probe, a second (“feedback”) probe, and a third(“start”) probe disposed within said waveguide body, the sourceoperating at a first frequency such that the waveguide body resonates ina relatively higher order resonant mode before the plasma is formed, andat a second frequency such that the waveguide body resonates in arelatively lower order resonant mode after the plasma reaches a steadystate, the first probe disposed near or at an electric field minimum ofthe higher order mode and not near an electric field minimum of thelower order mode, the second probe disposed anywhere except near anelectric field minimum of the lower order mode or the higher order mode,the third probe disposed anywhere except near an electric field minimumof the higher order mode, the first and third probes connected to saidsource output through a diplexer which separates said first and secondfrequencies, the second probe connected to said source input, therebymaintaining the first and third probes such that power reflected fromthe waveguide body back to the source is minimized both before theplasma is formed and after the plasma reaches said steady state.
 9. Thelamp of claim 2 wherein: said means for sealing the aperture comprises awindow sealed to said first waveguide outer surface in an inertatmosphere, using a ceramic seal; and said means for depositing thestarting gas and light emitter within the lamp chamber comprises: thelamp chamber bottom having a first hole therethrough; the waveguidehaving a second body side generally opposed to said first waveguide bodyside and having a second hole extending in a tapped bore through thewaveguide body terminating in said first hole; the waveguide bodypositioned within an atmospheric chamber containing the starting gas ator near a preselected lamp non-operating pressure; the light emitterdeposited in the lamp chamber through said bore and first hole; and aplug screwed into said bore.
 10. The lamp of claim 2 wherein: said meansfor sealing the aperture comprises a window sealed to said firstwaveguide outer surface in an inert atmosphere; and said means fordepositing the starting gas and light emitter within the lamp chambercomprises: the lamp chamber having a lower portion tapering in a neckterminating in a second aperture; the waveguide having a second bodyside generally opposed to said first waveguide body side and having asecond hole extending in a tapered bore through the waveguide body incommunication with the neck, forming a lip; the waveguide bodypositioned within an atmospheric chamber containing the starting gas ator near a preselected lamp non-operating pressure; the light emitterdeposited in the lamp chamber through said second hole, bore and secondaperture; and a plug fitted into said bore so that the plug contactssaid lip, effecting a mechanical seal.
 11. The lamp of claim 9 or 10wherein a material is deposited over said plug head to effect a finalseal.
 12. The lamp of claim 10 wherein said plug comprises a tip adaptedto extend within the lamp chamber, thereby creating a discontinuitywhich provides an electric field concentration point.
 13. The lamp ofclaim 2 wherein: said means for sealing the aperture comprises a windowsealed to said first waveguide outer surface in an inert atmosphere; andsaid means for depositing the starting gas and light emitter within thelamp chamber comprises: the lamp chamber bottom having a first holetherethrough; the waveguide having a second body side generally opposedto said first waveguide body side and having a second hole extending ina bore through the waveguide body in communication with said first hole;a tube having an end and made of a first dielectric material insertedthrough said second hole and into said bore so that said tube endextends through said first hole into the lamp chamber; a fill mixture ofstarting gas and light emitter deposited into the evacuated lamp chambervia the tube; and a rod made of a second dielectric material insertedinto the tube.
 14. The lamp of claim 13 wherein said first and seconddielectric materials are each selected from the group consisting ofglass and quartz.
 15. The lamp of claim 2 wherein: said means fordepositing the starting gas and light emitter within the lamp chambercomprises: the lamp chamber having a side with a first hole; said firstwaveguide body side having a second hole in communication with saidfirst hole; a tube having an end and made of a first dielectric materialinserted through said first and second holes so that said tube endpenetrates the lamp chamber; a fill mixture of starting gas and lightemitter deposited into the evacuated lamp chamber via the tube; and arod made of a second dielectric material inserted into the tube; andsaid means for sealing the aperture comprises a window sealed to saidfirst waveguide outer surface at a temperature which will not melt saidtube.
 16. The lamp of claim 15 wherein said first and second dielectricmaterials are each selected from the group consisting of glass andquartz.
 17. The lamp of claim 2 wherein: said means for depositing thestarting gas and light emitter within the lamp chamber comprises: thelamp positioned within an atmospheric chamber containing the startinggas at a pressure at or near the non-operating lamp pressure, and thelight emitter deposited in the lamp chamber; and said means for sealingthe aperture comprises: first and second clamps attached to said firstwaveguide body side; said first waveguide body side having an O-ringgroove circumscribing said aperture; and a window and an O-ringpre-positioned within the atmospheric chamber, the O-ring disposedwithin said groove, the window covering said aperture, the clampstightened so as to bring the window into pressing contact with theO-ring and said first waveguide outer surface.
 18. The lamp of claim 2wherein: said means for depositing the starting gas and light emitterwithin the lamp chamber comprises: the lamp positioned within anatmospheric chamber containing the starting gas at a pressure at or nearthe non-operating lamp pressure, and the light emitter deposited in thelamp chamber; and said means for sealing the aperture comprises: thelamp further comprising generally opposed first and second portionsgenerally orthogonal to said first waveguide body side and extending,respectively, in first and second upper portions each having an interiorsurface with a thread engaging a screw-type cap with a central holetherethrough; said first waveguide body side having an O-ring groovecircumscribing said aperture; and a window and an O-ring pre-positionedwithin the atmospheric chamber, the O-ring disposed within said groove,the window covering said aperture, the cap screwed so as to bring thewindow into pressing contact with the O-ring and said first waveguideouter surface.
 19. The lamp of claim 2 wherein: said means fordepositing the starting gas and light emitter within the lamp chambercomprises: the lamp positioned within an atmospheric chamber containingthe starting gas at a pressure at or near the non-operating lamppressure, and the light emitter deposited in the lamp chamber; and saidmeans for sealing the aperture comprises: said first waveguide body sidehaving a detail circumscribing said aperture and adapted to closelyreceive a seal preform; a window and a seal preform pre-positionedwithin the atmospheric chamber, and the seal preform placed in thedetail; the window positioned on top of the seal preform, and thewaveguide body in thermal contact with a cold surface; and a hot mandrelin pressing contact with the window.
 20. The lamp of claim 2 wherein:said means for depositing the starting gas and light emitter within thelamp chamber comprises: the lamp positioned within an atmosphericchamber containing the starting gas at a pressure at or near thenon-operating lamp pressure, and the light emitter deposited in the lampchamber; and said means for sealing the aperture comprises: said firstwaveguide body side having a detail circumscribing said aperture inwhich is disposed a first metalization ring and a seal preformsuperposed on said ring; and a window having a lower surface to which isattached a second metalization ring, the window positioned on top of theseal preform so that the seal preform is sandwiched between the firstand second metalization rings while heating means is applied to melt theseal preform.
 21. The lamp of claim 20 wherein said heating means isselected from the group consisting of a brazing flame, a laser, and aradio frequency coil.
 22. The lamp of claim 1, wherein an opticalelement is rigidly attached to a heatsink which closely receives thewaveguide body, and said element is generally aligned with said lampchamber aperture.
 23. The lamp of claim 22 wherein said optical elementis selected from the group consisting of a lens, a light pipe, and atube lined with a reflective material.
 24. The lamp of claim 1, whereinsaid waveguide body has a generally cylindrical shape and is receivedwithin a generally cylindrical bore of a generally cylindrical metallicheatsink.
 25. The lamp of claim 24 wherein a compliant, hightemperature, thermal interface material is interposed between thewaveguide body and heatsink.
 26. The lamp of claim 1, wherein saidwaveguide body has a generally cylindrical shape and is enclosed byfirst and second semi-cylindrical portions of a clamshell-type heatsink.
 27. The lamp of claim 4, further comprising: a PIN diodeattenuator connected to said feedback probe; and an RF power detectorconnected to said drive probe; the lamp further comprising a circuithaving an amplifier portion comprising a plurality of stages connectedbetween the PIN diode attenuator and RF power detector, and a controlportion connected to the PIN diode attenuator, the RF power detector,and an optical power detector.
 28. The lamp of claim 27, wherein saidamplifier portion comprises: (a) a high power amplifier stage connectedto the RF power detector; (b) a medium power amplifier stage connectedto the high power amplifier stage; and (c) a preamplifier stageconnected between the medium power amplifier stage and the PIN diodeattenuator.
 29. The lamp of claim 27, wherein said control portion actsin combination with said PIN diode attenuator to provide a low powermode in which the plasma is maintained at a power level insufficient forlight emission but sufficient to keep the fill mixture ionized.
 30. Thelamp of claim 27, wherein said control portion acts in combination withsaid PIN diode attenuator to shut down the lamp slowly so as to limitthermal shock to the lamp and promote easier lamp starting.
 31. The lampof claim 27, wherein said control portion acts in combination with saidPIN diode attenuator and said RF power detector to maintain a desiredpower level during lamp operation, even if the incoming power supplyvoltage changes due to variation in the power supply output.
 32. Thelamp of claim 27, wherein said control portion acts in combination withsaid PIN diode attenuator to control the output power at a high levelduring the early part of the lamp operating cycle, thereby vaporizingthe fill mixture more quickly than can be achieved at normal operatingpower.
 33. The lamp of claim 27, wherein said control portion acts incombination with said PIN diode attenuator and said optical powerdetector to maintain a preselected illumination level should powerconditions and lamp emission characteristics change.
 34. The lamp ofclaim 5, further comprising: a PIN diode attenuator connected to saidfeedback probe; and an RF power detector connected to said drive probe;the lamp further comprising a circuit having an amplifier portioncomprising a plurality of stages connected between the PIN diodeattenuator and RF power detector, and a control portion connected to thePIN diode attenuator, the RF power detector, and an optical powerdetector.
 35. The lamp of claim 34, wherein said amplifier portioncomprises: (a) a high power amplifier stage connected to the RF powerdetector; (b) a medium power amplifier stage connected to the high poweramplifier stage; and (c) a preamplifier stage connected between themedium power amplifier stage and the PIN diode attenuator.
 36. The lampof claim 34, wherein said control portion acts in combination with saidPIN diode attenuator to provide a low power mode in which the plasma ismaintained at a power level insufficient for light emission butsufficient to keep the fill mixture ionized.
 37. The lamp of claim 34,wherein said control portion acts in combination with said PIN diodeattenuator to shut down the lamp slowly so as to limit thermal shock tothe lamp and promote easier lamp starting.
 38. The lamp of claim 34,wherein said control portion acts in combination with said PIN diodeattenuator and said RF power detector to maintain a desired power levelduring lamp operation, even if the incoming power supply voltage changesdue to variation in the power supply output.
 39. The lamp of claim 34,wherein said control portion acts in combination with said PIN diodeattenuator to control the output power at a high level during the earlypart of the lamp operating cycle, thereby vaporizing the fill mixturemore quickly than can be achieved at normal operating power.
 40. Thelamp of claim 34, wherein said control portion acts in combination withsaid PIN diode attenuator and said optical power detector to maintain apreselected illumination level should power conditions and lamp emissioncharacteristics change.
 41. The lamp of claim 5, further comprising: aPIN diode attenuator connected between said feedback probe and a firstPIN diode switch; a circuit comprising an amplifier portion comprising aplurality of stages connected between a second PIN diode switch and saiddrive probe, and a control portion connected to the PIN diodeattenuator, the first and second PIN diode switches, and an opticalpower detector; and first and second bandpass filters connected inparallel to the first and second PIN diode switches, the filtersindependently selectable and switchable by the control portion.
 42. Thelamp of claim 41, wherein said amplifier portion comprises: (a) a highpower amplifier stage connected to said drive probe; (b) a medium poweramplifier stage connected to the high power amplifier stage; and (c) apreamplifier stage connected between the medium power amplifier stageand said second PIN diode switch.
 43. The lamp of claim 41, wherein saidcontrol portion acts in combination with said first and second PIN diodeswitches, said first and second bandpass filters, and said PIN diodeattenuator to: (a) operate the lamp only in that cavity modecorresponding to a preselected frequency band, so all amplifier portionpower is directed into this mode; (b) enable a first cavity mode forstarting the lamp; (c) enable a second cavity mode once the fill mixturegas has ionized and plasma has begun to form, so that the first andsecond cavity modes propagate through said waveguide body to ensure thatthe fill mixture remains a plasma; and (d) shut down the first cavitymode so that only the second mode, preselected for lamp operation,propagates.
 44. The lamp of claim 8, further comprising: a PIN diodeattenuator connected to said feedback probe; an RF power detectorconnected to said drive probe; a bipolar PIN diode switch connected tosaid start probe; and a filter connected to the PIN diode attenuator;the lamp further comprising a circuit having an amplifier portioncomprising a plurality of stages including a high power amplifier stageconnected between the filter and the RF power detector, and a controlportion connected to the PIN diode attenuator, the PIN diode switch, thehigh power amplifier stage, the RF power detector, and an optical powerdetector.
 45. The lamp of claim 44, wherein said amplifier portionfurther comprises: (a) a medium power amplifier stage connected betweenthe PIN diode switch and high power amplifier stage; and (b) apreamplifier connected between the filter and PIN diode switch.
 46. Thelamp of claim 44, wherein said control portion acts in combination withsaid PIN diode attenuator, PIN diode switch, filter, RF power detector,and optical power detector to: (a) send power to said start probe, whichis critically coupled when the lamp is off, until the fill mixturebecomes ionized; (b) route power to said high power amplifier stage oncethe gas becomes ionized; and (c) remove power to the start probe when apredetermined condition is met, so that the plasma is powered only bythe drive probe.